1. Field of the Invention
The present invention is directed to an alloy coated product with an Al-Zn-Si base alloy coat including an Al-Zn-Fe-Si alloy layer and a method for making the same.
2. Description of the Prior Art
A zinc coating is generally used to provide corrosion resistance to a ferrous-base material. However, higher corrosion resistance is required to use the ferrous material in severe corrosive environments, e.g., a salt damaged area such as a seaside, an area having an acid rain. From the point of view, many kinds of Al-Zn alloy coats were developed. The demands of the Al-Zn alloy coats are increasing because the Al-Zn alloy coats has more excellent corrosion resistance than the Zn coat. Japanese Patent Publication [KOKOKU] No. 63-63626 describes about a steel wire coated with an Al-Zn alloy containing 3 to 10 wt % of Al. Suzuki et al. Japanese patent early publication [KOKAI] No. 1-263255 also describes about the method of Al-Zn alloy coating, which comprises the steps of dipping an article into a molten bath of Zn at a bath temperature in a range of 480.degree. to 560.degree. C. to form an undercoat on the article, and subsequently dipping the undercoat into an alloy molten bath containing at least 1 wt % of Al at a bath temperature in a range of 390.degree. to 460.degree. C. to form an Zn-Al alloy coat on the undercoat. The alloy molten bath preferably includes 0.1 to 10 wt % of Al. In case of the Al content less PG,3 than 0.1%, a desired effect of Al, which is to greatly enhance corrosion resistance of the alloy coat, is not obtained. On the other hand, when the alloy molten bath includes more than 10 wt % of Al, a typical ferrous metal bath container and the article are given a harmful attack from molten metals of the alloy molten bath. However, when we think about a corrosion protective coat used under more severe corrosive conditions in the future, an alloy coat having more excellent corrosion resistance as compared with the Zn-Al alloy coat will be requested.